The research supported by this award will focus on neural plasticity that develops in the hippocampus as a result of behavioral learning, using classical conditioning of eyeblink in rabbit as a model system. Three specific issues with respect to this plasticity will be investigated. First, we will determine the multi-synaptic anatomical pathways through which learning-induced changes in the activity of hippocampal pyramidal neurons affects the cerebellum--a brain structure known to be involved in the formation of the conditioned eyeblink response. Second, we will use nonlinear systems analytic techniques to characterize functional properties of the hippocampus expressed only at the network level, i.e., properties emerging from the coordinated activity of all its subpopulations of neurons acting as a system. We then will investigate how those system properties are altered during eyeblink conditioning. Finally, we will investigate the contribution of brainstem noradrenergic and serotonergic inputs to changes in pyramidal cell activity that develop during classical conditioning.